Laminate structures and flexible packaging materials incorporating same

ABSTRACT

Embodiments of the present disclosure are directed to laminates comprising a uniaxially oriented first multilayer film comprising ethylene-based polymer, wherein the uniaxially oriented first multilayer film has a ratio of percent elongation at break in the cross direction to percent elongation at break in the machine direction of at least 2 to 1; a biaxially oriented second multilayer film adhered to the uniaxially oriented first multilayer film and comprising an ethylene-based polymer, wherein the biaxially oriented second multilayer film has a ratio of percent elongation at break in the machine direction to percent elongation at break in the cross direction of at least 2 to 1; and a third film adhered to the biaxially oriented second multilayer film such that the biaxially oriented second multilayer film is disposed between the uniaxially oriented first multilayer film and the third film, wherein the third film comprises an ethylene-based polymer.

TECHNICAL FIELD

Embodiments described herein relate generally to laminate structures,and more particularly relate to laminate structures for flexiblepackaging materials.

BACKGROUND

Large stand up pouches (SUP) for liquid or granular packaging of 2 to 5Liter (L) content are typically made of triplex laminates, and have astructure comprising Biaxially Oriented Polyethylene Terephthalate(BOPET)/Biaxially Oriented Polyamide (BOPA)/Polyethylene Sealant. Onecritical performance requirement is the drop test of the pouch, and aminimum drop height is specified under which the pouch should not breakif dropped. Laminate structures mentioned above have been used in themarket, however due to changing regulations and the increasing demand touse recyclable packaging, there is a desire to provide large SUP made ofmonomaterials, preferably polyethylene. While these polyethylenemono-material laminates are desirable from a recyclability standpoint,achieving the desired mechanical properties (e.g., heat seal strength)has been challenging.

Accordingly, there is a need for improved laminates and processes formaking these laminates for use in flexible packaging embodiments,wherein the laminates have the dual benefits of recyclability andmechanical strength.

SUMMARY

Embodiments of the present disclosure meet those needs by providinglaminates having recyclability and mechanical strength. The presentlaminates combine the benefits of biaxially oriented polyethylene (BOPE) films with that of uniaxially (machine direction) orientedpolyethylene films (MDO-PE) films and a third film (also called sealantfilm). The mechanical and thermal properties of the MDO/BOPE/sealanttriplex laminate beneficially enhances each other to provide a structurethat provides the required mechanical strength and the requiredrecyclability

Specifically, the high machine direction (MD) stiffness and tensilestrength of the MDO film and the low stiffness and tensile strength inthe cross direction (CD) is compensated by the low stiffness and tensilestrength of BOPE films in the MD direction and high stiffness andtensile strength in the CD direction. The resulting laminated film has abalanced MD and CD stiffness and tensile strength, and a good tensileelongation, to provide strong laminates to resist packaging abuse,specifically packaging abuse in drop tests.

According to at least one laminate embodiment, the laminate comprises auniaxially oriented first multilayer film comprising ethylene-basedpolymer having a density from 0.930 to 0.970 g/cm³ and a melt index (I₂)from 0.1 to 10 g/10 minutes, wherein the uniaxially oriented firstmultilayer film is oriented in the machine direction at a draw ratiogreater than 3:1 and less than 8:1, and wherein the uniaxially orientedfirst multilayer film has a ratio of percent elongation at break in thecross direction to percent elongation at break in the machine directionof at least 2 to 1. The laminate also comprises a biaxially orientedsecond multilayer film adhered to the uniaxially oriented firstmultilayer film and comprising an ethylene-based polymer having adensity from 0.900 to 0.962 g/cm³, wherein the biaxially oriented secondmultilayer film has a cross directional draw ratio larger than itsmachine direction draw ratio, and wherein the biaxially oriented secondmultilayer film has a ratio of percent elongation at break in themachine direction to percent elongation at break in the cross directionof at least 2 to 1. Moreover, the laminate comprises a third filmadhered to the biaxially oriented second multilayer film such that thebiaxially oriented second multilayer film is disposed between theuniaxially oriented first multilayer film and the third film, whereinthe third film comprising an ethylene-based polymer having a densityfrom 0.865 g/cm³ to 0.935 g/cm³ and a melt index (1₂) from 0.5 to 5 g/10minutes.

These and other embodiments are described in more detail in thefollowing detailed description.

DETAILED DESCRIPTION

Specific embodiments of the present application will now be described.The disclosure may, however, be embodied in different forms and shouldnot be construed as limited to the embodiments set forth in thisdisclosure. Rather, these embodiments are provided so that thisdisclosure will be thorough and complete, and will fully convey thescope of the subject matter to those skilled in the art.

Definitions

The term “polymer” refers to a polymeric compound prepared bypolymerizing monomers, whether of the same or a different type. Thegeneric term polymer thus embraces the term “homopolymer,” usuallyemployed to refer to polymers prepared from only one type of monomer aswell as “copolymer” which refers to polymers prepared from two or moredifferent monomers. The term “interpolymer,” as used herein, refers to apolymer prepared by the polymerization of at least two different typesof monomers. The generic term interpolymer thus includes copolymers, andpolymers prepared from more than two different types of monomers, suchas terpolymers.

“Polyethylene” or “ethylene-based polymer” shall mean polymerscomprising greater than 50% by mole of units which have been derivedfrom ethylene monomer. This includes polyethylene homopolymers orcopolymers (meaning units derived from two or more comonomers). Commonforms of polyethylene known in the art include Low Density Polyethylene(LDPE); Linear Low Density Polyethylene (LLDPE); Ultra Low DensityPolyethylene (ULDPE); Very Low Density Polyethylene (VLDPE); single-sitecatalyzed Linear Low Density Polyethylene, including both linear andsubstantially linear low density resins (m-LLDPE); Medium DensityPolyethylene (MDPE); and High Density Polyethylene (HDPE).

The term “propylene-based polymer,” as used herein, refers to a polymerthat comprises, in polymerized form, refers to polymers comprisinggreater than 50% by mole of units which have been derived from propylenemonomer. This includes propylene homopolymer, random copolymerpolypropylene, impact copolymer polypropylene, propylene/α-olefincopolymer, and propylene/α-olefin copolymer.

The term “LDPE” may also be referred to as “high pressure ethylenepolymer” or “highly branched polyethylene” and is defined to mean thatthe polymer is partly or entirely homopolymerized or copolymerized inautoclave or tubular reactors at pressures above 14,500 psi (100 MPa)with the use of free-radical initiators, such as peroxides (see forexample U.S. Pat. No. 4,599,392, which is hereby incorporated byreference). LDPE resins typically have a density in the range of 0.916to 0.935 g/cc.

The term “LLDPE”, includes both resin made using the traditionalZiegler-Natta catalyst systems as well as single-site catalysts,including, but not limited to, bis-metallocene catalysts (sometimesreferred to as “m-LLDPE”) and constrained geometry catalysts, andincludes linear, substantially linear or heterogeneous polyethylenecopolymers or homopolymers. LLDPEs contain less long chain branchingthan LDPEs and include the substantially linear ethylene polymers whichare further defined in U.S. Pat. Nos. 5,272,236, 5,278,272, 5,582,923and 5,733,155; the homogeneously branched linear ethylene polymercompositions such as those in U.S. Pat. No. 3,645,992; theheterogeneously branched ethylene polymers such as those preparedaccording to the process disclosed in U.S. Pat. No. 4,076,698; and/orblends thereof (such as those disclosed in U.S. Pat. No. 3,914,342 or5,854,045). The LLDPEs can be made via gas-phase, solution-phase orslurry polymerization or any combination thereof, using any type ofreactor or reactor configuration known in the art.

The term “MDPE” refers to polyethylenes having densities from 0.926 to0.935 g/cm3. “MDPE” is typically made using chromium or Ziegler-Nattacatalysts or using single-site catalysts including, but not limited to,bis-metallocene catalysts and constrained geometry catalysts, andtypically have a molecular weight distribution (“MWD”) greater than 2.5.

The term “HDPE” refers to polyethylenes having densities greater thanabout 0.935 g/cm3, which are generally prepared with Ziegler-Nattacatalysts, chrome catalysts or single-site catalysts including, but notlimited to, bis-metallocene catalysts and constrained geometrycatalysts.

As used herein, the term, “monomaterial” means that the laminatestructures are composed substantially of polyethylene, wherein“substantially” means at least 95 wt. % polyethylene, or at least 99 wt.% polyethylene, or at least 99.5 wt. % polyethylene, or at least 99.9wt. % based on the overall weight of the laminate structure.

“Multilayer structure” means any structure having more than one layer.For example, the multilayer structure may have two, three, four, five ormore layers. A multilayer structure may be described as having thelayers designated with letters. For example, a three layer structurehaving a core layer B, and two external layers A and C may be designatedas A/B/C.

The terms “flexible packaging” or “flexible packaging material”encompass various non-rigid containers familiar to the skilled person.These may include pouches, stand-up pouches, pillow pouches, or bulkbags bulk bags, pre-made packages or the like. Some typical end useapplications for flexible packages are for snack, dry food, liquid, orcheese packages. Other end use applications include, but are not limitedto, pet foods, snacks, chips, frozen foods, meats, hot dogs, andnumerous other applications.

The terms “comprising,” “including,” “having,” and their derivatives,are not intended to exclude the presence of any additional component,step or procedure, whether or not the same is specifically disclosed. Inorder to avoid any doubt, all compositions claimed through use of theterm “comprising” may include any additional additive, adjuvant, orcompound, whether polymeric or otherwise, unless stated to the contrary.In contrast, the term, “consisting essentially of” excludes from thescope of any succeeding recitation any other component, step orprocedure, excepting those that are not essential to operability. Theterm “consisting of” excludes any component, step or procedure notspecifically delineated or listed.

Reference will now be made in detail to laminate structure embodimentsof the present disclosure, specifically laminate structures used inflexible packaging materials.

Embodiments are directed to laminates comprising a uniaxially orientedfirst multilayer film comprising ethylene-based polymer having a densityfrom 0.900 to 0.962 g/cm³ and a melt index (I₂) from 0.1 to 10 g/10minutes. The uniaxially oriented first multilayer film, which may alsobe referred to herein as an MDO film or an MDO-PE film, is oriented inthe machine direction at a draw ratio greater than 1:1 and less than8:1. Moreover, the uniaxially oriented first multilayer film has a ratioof percent elongation at break in the cross direction to percentelongation at break in the machine direction of at least 2 to 1.

Additionally, the laminate comprises a biaxially oriented secondmultilayer film adhered to the uniaxially oriented first multilayerfilm. The laminate comprises an ethylene-based polymer having a densityfrom 0.900 to 0.962 g/cm³. The biaxially oriented second multilayer filmhas a cross directional draw ratio larger than its machine directiondraw ratio, and the biaxially oriented second multilayer film has awherein the biaxially oriented second multilayer film has a ratio ofpercent elongation at break in the machine direction to percentelongation at break in the cross direction of at least 2 to 1.

Furthermore, the laminate comprises a third film adhered to thebiaxially oriented second multilayer film such that the biaxiallyoriented second multilayer film is disposed between the uniaxiallyoriented first multilayer film and the third film. The third film, whichmay also described as a blown film polyethylene sealant film, comprisesan ethylene-based polymer having a density from 0.865 g/cc to 0.935 g/ccand a melt index (I₂) from 0.5 to 5 g/10 minutes.

Uniaxially Oriented First Multilayer Film

In one or more embodiments, the uniaxially oriented first multilayerfilm may include HDPE in at least one layer in order to provide heatresistance for the laminate during heat seal. In one or moreembodiments, the uniaxially oriented first multilayer film comprises atleast 10% by weight HDPE, or at least 15% by weight HDPE, or at least20% by weight HDPE. The uniaxially oriented first multilayer film mayinclude 95% by weight ethylene-based polymer, or 99% by weightethylene-based polymer, or 99.9% by weight ethylene-based polymer, or100% by weight ethylene-based polymer. The high density polyethylene ofthe uniaxially oriented first multilayer film may have a density of atleast 0.950 g/cc, or at least 0.950 g/cc, or at least 0.960 g/cc. Inother embodiments, the high density polyethylene may have a density from0.950 to 0.975 g/cc, or from 0.955 to 0.970 g/cc. Moreover, the highdensity polyethylene may have a melt index from 0.5 to 2 g/10 mins, orfrom 0.6 to 1 g/10 mins. Commercial Examples may include ELITE™ 5960Gfrom The Dow Chemical Company, Midland, Mich.

Various thicknesses are contemplated for the uniaxially oriented firstmultilayer film. In one embodiment, the uniaxially oriented firstmultilayer film has a thickness from 15 to 30 win.

In another embodiment, the uniaxially oriented first multilayer film maycomprise at least one outer layer having a high density polyethylenecomprising a density of at least 0.950 g/cc, and a melt index (I₂) from0.3 to 5 g/10 mins, at least one inner layer comprising anethylene-based polymer having a density less than 0.920 g/cc and a meltindex from 0.5 to 5 g/10 mins, and at least one intermediate layerdisposed between the at least one inner layer and the at least one outerlayer, the intermediate layer comprising an ethylene based polymerhaving a density greater than 0.930 g/cc.

The high density polyethylene in the outer layer may include the densityranges and melt index values provided above. The outer layer may have athickness of 2 to 10 μm, or from 2 to 4 μm.

As stated above, at least one inner layer comprising an ethylene-basedpolymer having a density less than 0.920 g/cc and a melt index from 0.5to 5 g/10 mins. In one or more embodiments, the inner layer may includea polyolefin plastomer having a density less than 0.900 g/cc, or lessthan 0.900 g/cc, or less than 0.890 g/cc, or less than 0.880 g/cc, orless than 0.875 g/cc. In further embodiments, the polyolefin plastomerof the inner layer has a density from 0.860 to 0.900 g/cc, or from 0.860to 0.885 g/cc, or from 0.865 to 0.875 g/cc. Moreover, the polyolefinplastomer of the inner layer has a melt index from 0.5 to 3 g/10 mins,or from 0.6 to 1.5 g/10 mins, or from 0.8 to 1.2 g/10 mins. CommercialExamples of the polyolefin plastomer may include AFFINITY™ 8100,AFFINITY™ 8200, AFFINITY™ 1880, and AFFINITY™ 1140, all of which areavailable from The Dow Chemical Company, Midland, Mich.

In some embodiments, for example, non-blocked asymmetric filmembodiments, it is contemplated that the inner layer comprises anadditional ethylene-based polymer blended with the polyolefin plastomer.Various embodiments are contemplated for the ethylene based polymer. Inone or more embodiments, the inner layer comprises a density greaterthan 0.910 g/cc and a melt index (I₂) from 0.5 to 5 g/10 mins. Suitablecommercial examples may include ELITE™ or INNATE™ polymers availablefrom The Dow Chemical Company, Midland, Mich. The inner layer may have athickness of 2 to 10 μm, or from 2 to 5 μm.

In the intermediate layer of the uniaxially oriented first multilayerfilm, the ethylene based polymer may have a density greater than 0.930g/cc, or greater than 0.935 g/cc. In other embodiments, theethylene-based polymer may have a density from 0.920 to 0.950 g/cc, orfrom 0.925 to 0.945 g/cc, or from 0.935 to 0.945 g/cc. Moreover, theethylene-based polymer of the intermediate layer may have a melt indexfrom 0.5 to 2 g/10 mins, or from 0.6 to 1 g/10 mins. Commercial Examplesmay include ELITE™ 5940ST from The Dow Chemical Company, Midland, Mich.The intermediate layer may have a thickness of 8 to 30 μm.

In yet another embodiment, the uniaxially oriented first multilayer filmmay include a propylene-based polymer. The propylene-based polymer maybe used alone or in combination with the embodiments described herein.The propylene-based polymer may have a density of 0.850 g/cc to 0.900g/cc, or 0.855 to 0.895. The propylene-based polymer may have a meltflow rate (MFR) of 1 to 25, or 1 to 10 g/10 mins. Various commercialembodiments are contemplated as suitable. These may include Vistamaxx™3000, Vistamaxx™ 3020FL, Vistamaxx™ 3588FL and Vistamaxx™ 6102/6102FL,which are produced by ExxonMobil. Additionally, VERSIFY™ 2000 andVERSIFY™ 2300 from The Dow Chemical Company, Midland, Mich. may also beutilized.

Various processing parameters are considered suitable for stretching inthe machine direction. For example, the uniaxially oriented firstmultilayer film may be oriented in the machine direction at a draw ratiogreater than 3:1 and less than 8:1, or at a draw ratio from 4:1 to 8:1.

As stated above, the uniaxially oriented first multilayer film has aratio of percent elongation at break in the cross direction to percentelongation at break in the machine direction of at least 2 to 1. Infurther embodiments, the ratio of the percent elongation at break in thecross direction to percent elongation at break in the machine directionis at least 3 to 1, or at least 5 to 1, or at least 8 to 1 for theuniaxially oriented first multilayer film. Said another way, theuniaxially oriented first multilayer film has percent elongation atbreak in the cross direction greater by at least 100% than the percentelongation at break in the machine direction, or greater by at least200%, or greater by at least 300%.

Biaxially Oriented Second Multilayer Film

It is contemplated that the biaxially oriented second multilayer filmmay be a monolayer film or a multilayer film. For example, the biaxiallyoriented second multilayer film can further comprise other layerstypically included in multilayer films depending on the applicationincluding, for example, sealant layers, barrier layers, tie layers,other polyethylene layers, etc. In one or more embodiments, thebiaxially oriented second multilayer film may have a thickness from 15to 100 μm, or from 15 to 40 μm. The biaxially oriented second multilayerfilm may include 95% by weight ethylene-based polymer, or 99% by weightethylene-based polymer, or 99.9% by weight ethylene-based polymer, or100% by weight ethylene-based polymer.

The ethylene-based polymer of the biaxially oriented second multilayerfilm may have a density from 0.915 to 0.940 g/cc, or from 0.920 to 0.935g/cc, or from 0.920 to 0.930 g/cc. The biaxially oriented secondmultilayer film may have a melt index from 0.5 to 2 g/10 mins, or from0.6 to 1 g/10 mins.

The biaxially oriented second multilayer film may comprise a linear lowdensity polyethylene (LLDPE). Suitable LLDPE's include Ziegler-Nattacatalyzed linear low density polyethylene, single site catalyzed(including metallocene) linear low density polyethylene (mLLDPE), andmedium density polyethylene (MDPE) so long as the MDPE has a density nogreater than 0.940 g/cm³ as well as combinations of two or more of theforegoing. The LLDPE may have a density and melt index (I₂) as definedby the ranges above. The biaxially oriented second multilayer film cancomprise greater than 50 weight percent LLDPE in some embodiments,greater than 60 weight percent in other embodiments, and greater than 70weight percent in other embodiments.

In some embodiments, the biaxially oriented second multilayer film canfurther comprise one or more additional polymers including, for example,a high density polyethylene, a low density polyethylene, an ultra-lowdensity polyethylene, a polyethylene plastomer, a polyethyleneelastomer, an ethylene vinyl acetate, or a combination thereof. In suchembodiments, the one or more additional polymers can be present in anamount less than 50 weight percent.

The biaxially oriented polyethylene film can further comprise one ormore additives as known to those of skill in the art such as, forexample, antioxidants, phosphites, cling additives, anti-static agents,pigments, colorants, fillers, or combinations thereof.

In one or more embodiments, the biaxially oriented second multilayerfilm is biaxially oriented using a tenter frame sequential biaxialorientation process. Such techniques are generally known to those ofskill in the art. In other embodiments, the polyethylene film can bebiaxially oriented using other techniques known to those of skill in theart based on the teachings herein, such as double bubble orientationprocesses. In general, with a tenter frame sequential biaxialorientation process, the tenter frame is incorporated as part of amultilayer co-extrusion line. After extruding from a flat die, the filmis cooled down on a chill roll, and is immersed into a water bath filledwith room temperature water. The cast film is then passed onto a seriesof rollers with different revolving speeds to achieve stretching in themachine direction. There are several pairs of rollers in the MDstretching segment of the fabrication line, and are all oil heated. Thepaired rollers work sequentially as pre-heated rollers, stretchingrollers, and rollers for relaxing and annealing. The temperature of eachpair of rollers is separately controlled. After stretching in themachine direction, the film web is passed into a tenter frame hot airoven with heating zones to carry out stretching in the cross direction.The first several zones are for pre-heating, followed by zones forstretching, and then the last zones for annealing.

In some embodiments, the biaxially oriented second multilayer film isoriented in the machine direction at a draw ratio from 2:1 to 6:1 and inthe cross direction at a draw ratio from 2:1 to 9:1. The biaxiallyoriented second multilayer film, in some embodiments, is oriented in themachine direction at a draw ratio from 3:1 to 5:1 and in the crossdirection at a draw ratio from 3:1 to 8:1.

The biaxially oriented second multilayer film has a cross directionaldraw ratio larger than its machine direction draw ratio, and thebiaxially oriented second multilayer film has a wherein the biaxiallyoriented second multilayer film has a ratio of percent elongation atbreak in the machine direction to percent elongation at break in thecross direction of at least 2 to 1. In further embodiments, the ratio ofpercent elongation at break in the machine direction to percentelongation at break in the cross direction is at least 3 to 1, or atleast 4 to 1 for the biaxially oriented second multilayer film. Saidanother way, wherein the biaxially oriented second multilayer film haspercent elongation at break in the machine direction greater by at least100% than percent elongation at break in the cross direction, or greaterby at least 200%, or greater by at least 300%.

Third Film

Like the biaxially oriented second multilayer film, the third film,which may also be called a sealant film or a blown sealant film, may bea multilayer film or a monolayer film. Unlike the uniaxially orientedand biaxially oriented films, it is contemplated that the sealant filmis not oriented in some embodiments. In further embodiments, the thirdfilm may have a Heat Seal Initiation temperature below 110° C., or below100° C. The third film may have a layer thickness from 40 to 100 μm, orfrom 60 to 80 μm.

The multilayer sealant film may include a plurality of layers comprisingethylene based polymer. In one embodiment, the third film comprises alinear low density polyethylene (LLDPE) having a density from 0.900 to0.930 g/cc and a melt index (I₂) from 0.5 to 5.0 g/10 mins. In furtherembodiments, the LLDPE may have a density from 0.905 to 0.925 g/cc, orfrom 0.910 to 0.925 g/cc. Moreover, the LLDPE may have a melt index (I₂)from 0.5 to 2.5 g/10 mins, or from 0.75 to 1.5 g/10 mins, or from 0.9 to1.2 g/10 mins. Additionally, the third film may comprise a low densitypolyethylene (LDPE) having a density from 0.915 to 0.935 g/cc and a meltindex (I₂) from 0.3 to 5.0 g/10 mins. In further embodiments, the LDPEmay have a density from 0.910 to 0.935 g/cc, or from 0.920 to 0.930g/cc. Moreover, the LDPE may have a melt index (I₂) from 0.5 to 2.5 g/10mins, or from 0.6 to 1.0 g/10 mins.

It is contemplated that one or more layers of the third film maycomprise a blend of LLDPE and LDPE. For example, the LLDPE/LDPE blendmay include at least 50% by weight, at least 60%, at least 70% byweight, or at least 80% by weight of LLDPE. Conversely, the LLDPE/LDPEblend may include from 1 up to 50% by weight, or up to 40% by weightLDPE, or up to 30% by weight, or up to 20% by weight LDPE.

In some embodiments, a first layer of the sealant film comprises atleast 30 percent by weight of a polyolefin plastomer, a polyolefinelastomer, an ultra-low density polyethylene, an ethylene acetatecopolymer, an ethylene acrylic acid copolymer, or an ethylene acrylatecopolymer.

When the sealant film comprises a polyolefin plastomer, the polyolefinplastomer can be a polyethylene plastomer or a polypropylene plastomer.Polyolefin plastomers include resins made using single-site catalystssuch as metallocenes and constrained geometry catalysts. The polyolefinplastomer has a density of 0.885 to 0.915 g/cc. All individual valuesand subranges from 0.885 g/cc to 0.915 g/cc are included herein anddisclosed herein, for example, the density of the polyolefin plastomercan be from a lower limit of 0.895, 0.900, or 0.905 g/cc to an upperlimit of 0.905, 0.910, or 0.915 g/cc. In some embodiments, thepolyolefin plastomer has a density from 0.890 to 0.910 g/cc.

In some embodiments, the polyolefin plastomer has a melt index (I₂) ofup to 20 g/10 minutes. All individual values and subranges up to 20 g/10minutes are included herein and disclosed herein. For example, thepolyolefin plastomer can have a melt index to an upper limit of 1.0,2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0, 9.0, 10.0, 11, 12, 13, 14, 15, 16,17, 18, 19, or 20 g/10 minutes. In a particular aspect, the polyolefinplastomer has an I₂ with a lower limit of 0.5 g/10 minutes. Examples ofpolyolefin plastomers that can be used in the sealant film include thosecommercially available from The Dow Chemical Company under the nameAFFINITY™ including, for example, AFFINITY™ PL 1881G and AFFINITY™PF1140G.

Adhesive Layers

Various adhesive compositions are considered suitable for the adhesivesused the laminate. These may include polyurethane, epoxy, acrylic, orthe like. In one embodiment, the laminate may comprises adhesive layerscomprising polyurethane adhesive. The polyurethane adhesive may besolventless, waterborne or solvent based. Furthermore, the polyurethaneadhesive may be a two part formulation.

The weight or thickness of the adhesive layer can depend on a number offactors including, for example, the desired thickness of the multilayerstructure, the type of adhesive use d, and other factors. In someembodiments, the adhesive layer is applied at up to 5.0 grams/m², o rfrom 1.0 to 4.0 g/m², or from 2.0 to 3.0 g/m².

Laminate

Without being limited by theory, the combination of the three filmsprovides an isotropic laminate. As used herein, “isotropic” means thelaminate has a percent elongation at break in the cross direction within30% of the percent elongation at break in the machine direction. Saidanother way, this means that the laminate yield similar tensile resultsin the MD direction or the cross direction. In further embodiments, thepresent laminates may have a percent elongation at break in the crossdirection within 25%, or within 20% of the percent elongation at breakin the machine direction. Moreover, the laminate may have a ratio ofpercent elongation at break in the machine direction to percentelongation at break in the cross direction ranging from 1.3:1 to 1:1.3,or from 1.2:1 to 1:1.2, or from 1.1:1 to 1:1.1.

Article

As stated above, the laminate may be included in a flexible packagingmaterial, such as a stand-up pouch.

Testing Methods

The test methods include the following:

Melt Index (I₂)

The Melt index (I₂) of the ethylene-based polymers was measured inaccordance to ASTM D-1238 at 190° C. at 2.16 kg. The values are reportedin g/10 min, which corresponds to grams eluted per 10 minutes.

Melt Flow Rate (MFR)

The Melt Flow Rate of the propylene-based polymers was measuredaccording to ASTM D-1238 at 230° C. and 2.16 kg. The values are reportedin g/10 min, which corresponds to grams eluted per 10 minutes.

Density

Samples for density measurement were prepared according to ASTM D4703and reported in grams/cubic centimeter (g/cc or g/cm³). Measurementswere made within one hour of sample pressing using ASTM D792, Method B.

Tensile Properties

Percent elongation, elongation at break, and force at break weredetermined in both the machine direction (MD) and cross direction (CD)in accordance with the ASTM D-882-method. The machine used was anInstron 5965 Tensile Tester and operated with a pulling speed of 500mm/min. The sample width was 1 inch.

Heat Seal Testing

To determine heat seal strength and heat seal initiation temperature,the samples were sealed by a J&B Hot Tack 4000 Tester. The sample widthwas 1 inch, the seal time was 0.5 seconds, and the seal pressure was0.275 N/mm². Then, the sealed samples were aged for 24 hours before heatseal strength was tested on an Instron 5965 Tensile Tester at a pullingspeed of 500 mm/min.

EXAMPLES

The following examples illustrate features of the present disclosure butare not intended to limit the scope of the disclosure.

Commercial Polymers Used

The following listed polymers were used in the experimental laminatesdescribed below. All of the polymers are produced by The Dow ChemicalCompany, Midland, Mich. Additionally, the laminate examples utilized thefollowing 2 commercially available adhesives available from The DowChemical Company, Midland, Mich. The first adhesive is MOR-FREE™L75-300+MF L75-300+CR88-300 (hereinafter “MOR-FREE”), which is a twopart solventless polyurethane adhesives. The second adhesive is ADCOTE™675A+675C (hereinafter “ADCOTE”), which is a solvent-based two-componentpolyurethane adhesive.

The polymer synthesis for LLDPE 1 is provided after Table 1.

TABLE 1 Polymer Density (g/cc) Melt Index (g/10 mins) ELITE ™ 5940ST0.941 0.85 ELITE ™ 5960G 0.96 0.85 AFFINITY ™ EG 8100G 0.870 1.0 LLDPE 10.916 1.05 LDPE 310E 0.924 0.75

Synthesis of LLDPE 1

LLDPE 1 is an ethylene-hexene copolymer prepared via solutionpolymerization process in a single reactor in the presence of a catalystsystem comprising a metal complex of a polyvalent aryloxyether having amelt index (I2) of 1.05 g/10 minutes, a density of 0.916 g/cm3, a CEFfraction from 70 to 90° C. of 90.3%, an 1₁₀/1₂ of 7.3. Inventivecomposition 1 is prepared via solution polymerization in a single loopreactor system as described in U.S. Pat. No. 5,977,251 in the presenceof a Zirconium based catalyst system (“Post-Metallocene Catalyst”)comprising[2,2′″-[1,3-propanediylbis(oxy-κO)]bis[3″,5,5″-tris(1,1-dimethylethyl)-5′-methyl[1,1′:3′,1″-terphenyl]-2′-olato-κO]]dimethyl-, (OC-6-33)-Zirconium, represented by thefollowing formula:

The polymerization conditions for LLDPE 1 are reported in Tables 2 and3. Referring to Table 3, TEA is triethylaluminum and PETROSOL D 100/120is solvent which is commercially available from CEPSA (Compañía Españolade Petroleos, S.A.U., Madrid, Spain).

TABLE 2 1. REACTOR FEEDS Units LLDPE 1 Reactor Solvent/Ethylene Feed g/g4.04 Flow ratio Solvent Type Used PETROSOL D 100/120 Comonomer Type Used1-Hexene Reactor Comonomer/Ethylene Feed g/g 0.263 Flow ratio ReactorFresh Hydrogen/ethylene g/kg 0.058 Feed Flow ratio Reactor ControlTemperature ° C. 160 Reactor Pressure (gauge) Bar 52 Reactor EthyleneConversion % 86.9 Reactor Residence Time Min 6.5 Recycle Ratio 4.2

TABLE 3 2. CATALYST LLDPE 1 Reactor Co-Catalyst-1/Catalyst Molar feed2.0 Ratio Reactor Co-Catalyst-1 Type bis(hydrogenated tallowalkyl)methyl, tetrakis(penta- fluorophenyl)borate(1-) amine ReactorCo-Catalyst-2/Catalyst Molar 42 Ratio Reactor Co-Catalyst-2 Type TEA

Fabrication of BOPE Films

Referring to Table 4 below, BOPE Samples 1, 2 and 3 are commercial BOPEproducts from Decro, specifically DL25 for 25 μm BOPE Sample 1, DL30 for30 μm BOPE Sample 2, and DL50 for 50 μm BOPE Sample 3. The DL25, DL30and DL50 BOPE films include a polyethylene polymer with a density of0.925 g/cc

As shown in Table 4, these BOPE Samples of various thicknesses werestudied. The data illustrates that in MD direction of the film, thetensile curve is rather flat shows high elongation at break. The CDtensile direction was very stiff and had low elongation at break. Thisasymmetric difference in MD and CD tensile behavior is not beneficialfor drop test resistance. In addition, the thermal resistance of thisBOPE film was lower than desired, and shrinkage could occur when thefilm is heated above 130° C.

TABLE 4 Elongation Elongation at Break Stress at at Break Stress at BOPEThickness MD Break MD CD Break CD Sample (μm) (%) (MPa) (%) (MPa) Sample1 25 262 111.4 50 240.4 Sample 2 30 341 147.1 60 266.1 Sample 3 50 356110.2 61 188.8

Fabrication of MDO Films

Referring to Table 5 below, an MDO film (MDO Sample 1) was prepared on ablown film MDO line at a draw ratio of 6.5. The die head had a 400 mmdiameter with output of 448 kg/h, and a final winding speed of 226m/min. The Blow Up Ratio (BUR) used was 2.6 (layflat before stretchingwas 1650 mm). The primary film thickness (before blocking) was 64 μm.The secondary film thickness (after stretching) was 25 μm. (600%stretching). The die temperature was 200° C., except for 210° C. in thelast two zones. Extrusion temperatures were all set at 200° C.

TABLE 5 Thickness Thickness MDO Sample Before After 1 Layer StretchingStretching Structure Composition (μm) (μm) A ELITE 5960G 18 3 B ELITE5940ST 30 5 C AFFINITY 8100G 12 2 C AFFINITY 8100G 12 2 B ELITE 5940ST30 5 A ELITE 5960G 18 3

The film tensile behavior of the MDO Sample 1 film is listed in thefollowing Table 6. As shown, the MDO film had high elongation at breakin the CD direction but was much stiffer in the MD direction asdemonstrated by a much lower elongation at break. Thus, it compensatedfor the tensile properties of the BOPE film.

TABLE 6 Elongation Force at Stress at Elongation Force at Stress at MDOThickness at Break MD Break MD Break MD at Break CD Break CD Break CDSample (μm) (%) (N) (MPa) (%) (N) (MPa) Sample 1 20 18% 49.86 184.65441% 4.80 17.76

Third Film (Sealant Film)

The above two films were then laminated to a sealant film web made of acoextruded PE film, which had the tensile properties shown in Table 7below. As shown, the tensile properties of the 70 μm sealant film areisotropic as demonstrated by an essentially equivalent elongation atbreak in the MD and CD directions.

TABLE 7 Elongation Stress at Elongation Stress at at Break Break atBreak Break BOPE Thickness MD MD CD CD Sample (μm) (%) (MPa) (%) (MPa)Sealant Film 70 645 40.7 654 36.6

The 70 μm sealant film was produced on an Alpine Blown film line with a200 mm die, and a BUR of 2.5. The film had a coextruded ABC three layerstructure as follows: A=80% by weight LLDPE 1+20% by weight LDPE 310E;B=LLDPE 1+20% LDPE 310E; and C=80% by weight LLDPE 1+20% LDPE 310E.

Laminate Procedure

For the lamination process, a Nordmeccanica™ Labo Combi 400 laminatorwas used. For the Inventive Triplex Samples 1 and 2 in Table 8, theadhesive was applied onto one surface of the BOPE film using a typicaldoctor blade, after which the second film (MDO Sample 1 film) waspressed against the BOPE film at a nip region to produce a duplexlaminate. An adhesive was then applied on the duplex laminate,specifically applied on the opposite surface of the BOPE film. At whichpoint, the duplex laminates were pressed against the sealant film toproduce the Inventive Triplex Laminates. The Comparative TriplexLaminates were produced in the same manner albeit with different filmcombinations and compositions than the specific film combinations ofInventive Triplex Samples 1 and 2.

Triplex Laminate Examples

TABLE 8 Elongation Stress at Elongation Stress at at Break Break atBreak Break Triplex Laminate MD MD CD CD Sample Structure (%) (MPa) (%)(MPa) Inventive MDO Sample 47 52.57 73 39.15 Triplex 1/ADCOTE/ Sample 1BOPE Sample 1/ADCOTE/ PE Sealant Film Inventive MDO Sample 48 52.8 6344.36 Triplex 1/MOR-FREE/ Sample 2 BOPE Sample 1/MOR-FREE/ PE SealantFilm Comparative BOPP* (20 μm 108 32.38 31 65.02 Triplex thickness)/Sample 1 ADCOTE/ BOPE Sample 1/ADCOTE/ PE Sealant Film ComparativeBOPET** (12 98 78.09 83 62.81 Triplex μm thickness)/ Sample 2 ADCOTE/BOPA*** (15 μm thickness)/ ADCOTE/PE Sealant Film *BOPP is BiaxiallyOriented Polypropylene **BOPET is Biaxially Oriented PolyethyleneTerephthalate ***BOPA is Biaxially Oriented Polyamide

As shown above in Table 8, the Inventive Triplex Laminates 1 and 2 wereisotropic, which is this case means that the percent elongation at breakin the machine and cross directions deviated by less than 30%. TheInventive Triplex Laminates 1 and 2 outperforms Comparative TriplexSample 1, which includes BOPP instead of BOPE, since Comparative TriplexSample 1 has a percent elongation at break of 108% in the machinedirection and 31% in the cross direction. Thus, Comparative TriplexSample 1 was clearly not an isotropic film. Moreover, Inventive TriplexLaminates 1 and 2 performs comparably from an isotropic standpoint toComparative Triplex Sample 2, which includes BOPET and BOPA instead ofonly polyethylene materials; however, Inventive Triplex Laminates 1 and2 achieved that desired isotropic performance with a more easilyrecyclable polyethylene monomaterial laminate.

Referring to Table 10 below, the Inventive Triplex Laminates 1 and 2were compared against the Comparative Triplex Samples 1 and 2 as well asComparative Triplex Samples 3 and 4 in Table 9.

TABLE 9 Comparative BOPET** (12 μm thickness)/ADCOTE/BOPE Sample 1/Triplex 3 ADCOTE/PE Sealant Film Comparative BOPET** (12 μmthickness)/ADCOTE/BOPP* (20 μm Triplex 4 thickness)/ADCOTE/PE SealantFilm

TABLE 10 Heat Seal Strength Comparative Comparative ComparativeComparative Inventive Inventive Temp. Triplex 1 Triplex 2 Triplex 3Triplex 4 Triplex 1 Triplex 2 (° C.) (N/15 mm) (N/15 mm) (N/15 mm) (N/25m) (N/25 m) (N/25 m) 90 0 0 0 0 0 0 100 2.936 4.584 4.53 5.47 4.8125.946 105 16.234 19.94 19.586 12.386 17.138 16.162 110 28.164 57.1230.104 32.418 21.712 39.616 115 38.862 67.28 32.484 39.438 24.346 43.636120 32.234 54.854 35.336 44.86 30.87 51.132 130 36.698 68.75 32.89647.45 35.218 51.6 140 48.392 67.41 38.864 43.544 37.68 53.606 150 52.6573.554 43.07 47.186 44.342 55.552 160 56.532 70.246 42.256 50.484 44.98250.716

For the heat sealing of the triplex laminates, it is desirable to haveat least a 30 N heat seal strength throughout the sealing temperaturewindow of 120-150° C. As shown in Table 10, the Inventive TriplexLaminates 1 and 2 met this requirement and thus performed comparably tothe conventional Comparative Triplex Laminates 1-4; however, all of theComparatives were not monomaterial polyethylene laminates like theInventive Laminates and thus cannot achieve the desired recyclability.Only the monomaterial Inventive Triplex Laminates can achieve thedesired heat seal strength, while also providing recyclability benefits.

It will be apparent that modifications and variations are possiblewithout departing from the scope of the disclosure defined in theappended claims. More specifically, although some aspects of the presentdisclosure are identified herein as preferred or particularlyadvantageous, it is contemplated that the present disclosure is notnecessarily limited to these aspects.

1. A laminate comprising: a uniaxially oriented first multilayer filmcomprising ethylene-based polymer having a density from 0.930 to 0.970g/cm³ and a melt index (I2) from 0.1 to 10 g/10 minutes, wherein theuniaxially oriented first multilayer film is oriented in the machinedirection at a draw ratio greater than 3:1 and less than 8:1, andwherein the uniaxially oriented first multilayer film has a ratio ofpercent elongation at break in the cross direction to percent elongationat break in the machine direction of at least 2 to 1; a biaxiallyoriented second multilayer film adhered to the uniaxially oriented firstmultilayer film and comprising an ethylene-based polymer having adensity from 0.900 to 0.962 g/cm³, wherein the biaxially oriented secondmultilayer film has a cross directional draw ratio larger than itsmachine direction draw ratio, and wherein the biaxially oriented secondmultilayer film has a ratio of percent elongation at break in themachine direction to percent elongation at break in the cross directionof at least 2 to 1; and a third multilayer film adhered to the biaxiallyoriented second multilayer film such that the biaxially oriented secondmultilayer film is disposed between the uniaxially oriented firstmultilayer film and the third film, wherein the third film comprising anethylene-based polymer having a density from 0.865 g/cm³ to 0.935 g/cm³and a melt index (I2) from 0.5 to 5 g/10 minutes.
 2. The laminate ofclaim 1, wherein the third film has a Heat Seal Initiation temperaturebelow 100° C.
 3. The laminate of claim 1, wherein the uniaxiallyoriented first multilayer film has percent elongation at break in thecross direction greater by at least 100% than percent elongation atbreak in the machine direction, and wherein the biaxially orientedsecond multilayer film has percent elongation at break in the machinedirection greater by at least 100% than percent elongation at break inthe cross direction.
 4. The laminate of claim 1, wherein the ratio ofpercent elongation at break in the cross direction to percent elongationat break in the machine direction of at least 3 to 1 for the uniaxiallyoriented first multilayer film, and has a ratio of percent elongation atbreak in the machine direction to percent elongation at break in thecross direction of at least 3 to 1 for the biaxially oriented secondmultilayer film.
 5. The laminate of claim 1, wherein the uniaxiallyoriented first multilayer film has a thickness from 15 to 30 μm, thebiaxially oriented second multilayer film has a thickness of 15 to 100μm, and the third film has a layer thickness from 40 to 100 μm.
 6. Thelaminate of claim 1, wherein the uniaxially oriented first multilayerfilm comprises: at least one outer layer having a high densitypolyethylene comprising a density of at least 0.950 g/cc, and a meltindex (I₂) from 0.3 to 5 g/10 mins; at least one inner layer comprisingan ethylene-based polymer having a density less than 0.920 g/cc and amelt index from 0.5 to 5 g/10 mins; and at least one intermediate layerdisposed between the at least one inner layer and the at least one outerlayer, the intermediate layer comprising an ethylene based polymerhaving a density greater than 0.930 g/cc.
 7. The laminate of claim 6,wherein the at least one inner layer comprises a polyolefin plastomerhaving a density less than 0.900 g/cc and a melt index from 0.5 to 5g/10 mins.
 8. The laminate of claim 1, wherein the uniaxially orientedfirst multilayer film comprises at least 10% by weight HDPE.
 9. Thelaminate of claim 1, wherein the ethylene-based polymer of the biaxiallyoriented second multilayer film has a density of 0.915 to 0.940 g/cc,and a melt index from 0.5 to 2.0 g/10 mins.
 10. The laminate of claim 1,wherein the third film is a multilayer film, the multilayer film havinga plurality of layers comprising ethylene based polymer.
 11. Thelaminate of claim 1, wherein the third film comprises a linear lowdensity polyethylene having a density from 0.900 to 0.930 g/cc and amelt index (I₂) from 0.5 to 5.0 g/10 mins.
 12. The laminate of claim 1,wherein the third film comprises a low density polyethylene having adensity from 0.915 to 0.935 g/cc and a melt index (I₂) from 0.3 to 3.0g/10 mins.
 13. The laminate of claim 1, wherein the laminate comprisesadhesive layers comprising polyurethane adhesive.
 14. The laminate ofclaim 1, wherein the laminate has a ratio of percent elongation at breakin the machine direction to percent elongation at break in the crossdirection from 1.3:1 to 1:1.3.